1. Field of the Invention
The present invention relates to a medical endoscope equipped with a cleaning device for cleaning a viewing window of an insertion section.
2. Description of Related Art
A medical endoscope is generally made up of an insertion section including a bending section and a viewing head which is adapted for insertion into a human body cavity, an operating section connected to the viewing head through a flexible section and a light guide section through which the viewing head is connected to a light source unit. The viewing head, which is located right after the bending section, is provided with a viewing system comprising an illumination system for illuminating the inside of a human body cavity and an image pickup system including an imaging lens system for picking up a local image of the cavity interior under illumination. The illuminating system includes a light guide fiber bundle and an illumination lens system mounted, directly or through a protective glass plate, in an illumination window which is located immediately after a light exit end of the light guide fiber bundle. The image pickup system includes an image guide fiber bundle or a solid state imaging device such as a charge coupled device (CCD) and an objective or image forming lens system mounted, directly or through a protective glass plate, in an image viewing window adjacent to the illumination window for focusing an image of the interior of the human body cavity under illumination upon a light receiving surface of the light guide fiber bundle or the solid state imaging device.
When the viewing window gets dirty with body liquid which generally stagnates in a human body cavity into which the medical endoscope is inserted, the field of view of the endoscope gets dark and unclear. For this reason, the medical endoscope is typically provided with a structure for cleaning the viewing window in which the foremost lens element of the image forming lens system or the protective glass plate is located during observation and/or examination of a human body cavity. Cleaning the viewing window is implemented by injecting cleaning liquid or rinse water against the viewing window to wash dirt off and then blowing pressurized air against the viewing window. For the cleaning structure the endoscope is necessarily provided with an air feed channel and a water feed channel, both of which extend separately from the operating section to the distal end, or otherwise which extend separately halfway from the operating section and join into a common air/water feed channel to the distal end. In the medical endoscope provided with the air feed channel and the water feed channel incorporated separately all along the way or in the form of partly joined fashion, the cleaning liquid flows along an axial line of the viewing head and on the other hand, the image forming lens system is positioned in the viewing head with the optical axis placed perpendicularly to an extreme end plane of the viewing head, the air feed channel and the water feed channel have to turn at approximately 90xc2x0 so as to direct the cleaning fluid toward the viewing window. On the grounds of the cleaning structure, the medical endoscope is typically equipped with a feeding nozzle at the extreme end of the viewing head. Usually, the feeding nozzle extends out of the extreme end of the viewing head and surrounds completely ports of the air feed channel and water feed channel or an outlet of the water/air feed channel. The feeding nozzle has a thin slot nozzle hole which is directed toward the lens element of the image forming lens system so as to force cleaning water/air to flow along the distal end of the viewing head. As is apparent, since the feeding nozzle works to cause a turnaround of a fluid flow and receives pressure from the fluid flow at the turning point, the nozzle has to be firmly secured to the viewing head, which is essential in order to prevent the feeding nozzle from coming off in the human body cavity.
Cleaning and sterilization of the medical endoscope after each observation and/or examination is essential in view of preventing secondary infection. For the same reason, cleaning and sterilization of the inside of the feed channel is also essential. Cleaning the air feed channel and the water feed channel may be done with a channel cleaning brush. However, in the case where the feed channel is provided with an feeding nozzle, there is the necessity of removing the feeding nozzle before inserting the channel cleaning brush into the air feed channel or the air feed channel, which is quit troublesome work.
There has been a medical endoscope that is equipped with a viewing head cap having a feeding nozzle integrally formed therewith. In addition to the requirement that the nozzle equipped viewing head cap is easily put on and off from the viewing head, there is the somewhat conflicting requirement that it is configured so as to be hard to come off from the viewing head during observation and/or examination. Further, it is required that the feeding nozzle direct fluid flow, in particular a pressurized flow, precisely toward the foremost lens surface of the image forming lens system or the protective glass plate. In compliance with these requirements, the viewing head is construed by a cylindrical rubber ring for surrounding the distal end section thereof and a spray nozzle which is made of a hard plastic for the reason of stable directivity of cleaning liquid sprayed from the nozzle. One of such endoscopes is known from, for example, Japanese Unexamined Patent Publication No. 8-140923. Some endoscopes, such as having been proposed in Japanese Utility Model Publication No. 6-41530, have plastic viewing head hoods. The hood has an integral feeding nozzle that is located in a position opposite to a suction opening with respect to a viewing window so as to cover an opening of a fluid feed channel and injects cleaning fluid toward the viewing window. The hood is formed with a groove extending from the feeding nozzle to the suction opening through which cleaning fluid injected by the feeding nozzle is sucked into a suction channel. This hood provides reliable injection of cleaning liquid over the viewing window and reliable suction of the cleaning liquid. The viewing head cap or the viewing head hood that is formed integrally with a feeding nozzle and detachably put on the viewing head makes it easy to wash and clean the cleaning liquid feed channel.
The nozzle equipped viewing head cap that has been disclosed in Japanese Unexamined Patent Publication No. 8-140923 can provide a stable nozzle configuration which is desirable for directing a stream of cleaning liquid accurately toward the viewing window and washing the viewing window effectively, and is easily and reliably put on the viewing head. However, the nozzle equipped viewing head cap has to be prepared by integrating two pieces made of materials different in quality, so as to be inferior in terms of productivity and production costs. On the other hand, while the nozzle equipped viewing head hood that has been disclosed in Japanese Utility Model Publication No. 6-41530 can provide an enhanced effect of cleaning the viewing window and, in particular, effective removal of water drops from the viewing window because of suction of cleaning liquid through the suction opening, however, the nozzle equipped viewing head hood has a necessity of arranging the feeding nozzle so as to be on a straight line crossing the viewing window and the suction opening, which imposes restraints on the lay-out of necessary parts and elements of the viewing head, it is difficult to make the insertion section slender.
It is therefore an object of the present invention to provide a medical endoscope that makes the structure of a feeding nozzle simple and is possible to wash dirt and liquid drops off from a viewing window without being affected by the arrangement of various related parts and elements of a viewing head.
The above object is accomplished by a medical endoscope having an insertion section including a viewing head which is connected to an operating section through a flexible section and includes an illumination system located behind an illumination window, a viewing lens system located behind a viewing window, fluid feed means through which at least cleaning fluid is fed to the viewing window, and suction feed means through which suction is applied to a distal end of the viewing head, which comprises a cylindrical viewing head casing for housing the illumination system, the viewing lens system, and the fluid feed means therein; an annular-shaped viewing head cap detachably fitted to the generally cylindrical viewing head casing, the viewing head cap being formed so as to have an generally cylindrical wall extending a predetermined height from a distal end of the viewing head casing in a lengthwise direction of the insertion section, a fluid feeding nozzle having an injection port through which the cleaning fluid fed through the fluid feed means is injected, the fluid feeding nozzle being formed integrally with the generally annular-shaped viewing head cap and configured to form a fluid path which is brought into communication with the fluid feed means when the generally annular-shaped viewing head cap is fitted to the generally cylindrical viewing head casing and turn to direct the cleaning fluid through the fluid feed means toward the viewing window; and a drain path opening to a space formed between the cylindrical wall of the generally annular-shaped viewing head cap and the distal end of the viewing head at one of opposite ends thereof and being in communication with the suction feed means at another of the opposite ends so that liquid that stays in the space is sucked through the drain path into the suction feed means. Specifically, the drain path comprises a drain port having a predetermined opening angle at a location opposite to the injection port of the fluid feeding nozzle, a drain ditch which is formed between a groove formed in the generally cylindrical wall of the generally annular-shaped viewing head cap and the generally cylindrical viewing head casing so as to be in communication with the drain port, and a communication path through which the drain path is communicated with the suction feed means.
The fluid feed means may comprise a cleaning water feed channel and an air feed channel separately extending from the viewing head to the operating section, or otherwise, the fluid feed means may comprise a cleaning water feed channel and an air feed channel separately extending in the insertion section and joining together in the flexible section. In terms of easy cleaning, the medical endoscope is preferred to have no diverging section in the fluid feed means.
The viewing head casing may be formed with a recess in its distal end so that the fluid feed means, more specifically the cleaning water feed channel and the air feed channel opens in the recess and the fluid feeding nozzle is fitted in the recess.
The drain port is preferably configured so as to extend in conformity with or covering a spread angle of fluid injected by the fluid feeding nozzle.